The metallization of a non-conductor generally requires a catalyst to be placed beforehand on the surface of the non-conductor, and coating metal is triggered to be deposited at the location of the catalyst in an electroless (chemical plating) plating solution. Normally catalysts such as tin palladium (Sn—Pd) colloid do not adhere to a hydrophobic surface, which then requires hydrophilic modification for the substrate surface to be plated. For instance, a glass substrate may be thoroughly cleaned in a strong acid, or a polymer substrate needs to be soaked in a high-temperature solution of caustic soda for a certain period of time. Not only are these processes time-consuming and complicated in nature, the strong acids and strong bases are dangerous, which raises many health and safety concerns for those performing the processes as the materials must be handled in an environment equipped with a smoke venting cabinet.
A relatively effective method for hydrophilic or hydrophobic property modification of the substrate surface is using plasma, such as capacitance-coupled plasma (CCP) in which a sample is placed in a reaction chamber. However, since the volume of the reaction chamber is large, it requires a long period of time to pump out air for getting a sufficiently low pressure, and therefore consumes great amount of energy. Moreover, such manner of treatment lacks selectivity of surface to be treated. Another configuration of CCP is parallel-plate CCP, wherein the sample is placed between two parallel electrodes thus resembling a sandwich configuration. However, for both of the above configurations, the bombardment of plasma all directly occurs on the treated surface may be resulting in etching or undesired roughening of the surface which sometimes might not be tolerated for certain applications.
In case a process of electrochemical plating on a non-conductive substrate requires patterning, then a catalyst must be patterned beforehand. A subtractive method such as masking with an adhesive tape might quickly met the patterning need, but most tapes withstand only short periods of soaking in an alkaline solution and such a method is incapable of providing a fine resolution. Therefore, to develop a technique which effectively modify functional-group properties on an object surface at room temperature is needed.